This invention relates to masks for manufacturing semiconductor chips and to methods for fabricating masks used in the manufacture of semiconductor chips, and particularly to X-ray masks and their fabrication.
The current procedure for fabricating X-ray masks involves:
Growing a boron doped layer on a semiconductor substrate, bonding a glass ring to the substrate.
Etching away the substrate with an etchant that does not appreciably etch the boron doped epitaxial layer.
Metallizing the silicon side of the wafer composite.
Applying a resist, exposing the pattern, and developing.
Plating gold to a desired thickness.
Stripping the resist.
The order of these steps may vary depending upon the yield at various steps.
This technique usually includes controlling the stress in the resulting diaphragm by incorporating germanium in the epitaxial layer. This and the very high level of boron needed to insure an adequately low etch rate of the boron doped layer tends to generate defects in the silicon. They can also lead to irregularities in the thickness of the final membranes.